Microlens Array Optical Relay for Compact Imaging
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Solution Overview
Problem
Conventional optical relay systems, such as those using graded index rod lenses, are often bulky and inefficient due to their large total conjugate length, which limits their application in compact devices like smartphones and tablets, and they suffer from losses and distortions due to diffraction and phase errors.
Innovation Solution
The use of microlens arrays (MLAs) in a compact stack configuration with in-tandem pairs that implement full Fourier transforms, providing phase correction and minimizing losses by stitching conelets of light into a complete numerical aperture without gaps, thus achieving high-efficiency imaging with a thin form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional optical relay systems using graded index rod lenses are used, then imaging function is achieved, but the system becomes bulky with large total conjugate length
Solution Approach 1:
The optical relay system is segmented into multiple discrete microlens arrays (MLAs) arranged in a compact stack configuration. Each MLA consists of multiple lenslets that collectively perform the relay function, replacing the continuous graded index rod lens structure. This segmentation enables a reduced total conjugate length while maintaining imaging functionality.
Solution Approach 2:
The patent transitions from a single-dimensional rod lens structure to a multi-dimensional stacked array configuration of microlens arrays. By arranging MLAs in multiple layers along the optical axis with precise spacing, the system achieves compact volumetric integration that reduces the overall conjugate length while preserving the relay imaging function.
2Reliability
If conventional optical relay systems are used, then imaging is achieved, but losses and distortions occur due to diffraction and phase errors
Solution Approach 1:
The patent introduces intermediate transform planes between pairs of microlens arrays where Fourier transforms occur. These intermediate planes act as mediators that enable phase correction between lenslet arrays, reducing phase errors and improving imaging efficiency. The Fourier transform relationship between adjacent MLAs and intermediate planes allows for controlled light propagation that minimizes diffraction losses.
3Manufacturing precision
If conventional optical relay systems are used, then imaging function is provided, but the system lacks phase correction capability
Solution Approach 1:
The phase correction function is segmented across multiple microlens arrays in the stack, with each MLA contributing to the overall phase correction through its specific positioning and focal length characteristics. This distributed phase correction approach achieves high phase accuracy without requiring a single complex phase-correcting element.
Solution Approach 2:
The microlens arrays serve multiple functions simultaneously: they perform relay imaging, provide phase correction, and enable Fourier transforms between intermediate planes. This multi-functionality reduces the need for separate dedicated components, managing system complexity while achieving precise phase control.
4Volume of moving object
If compact stack configuration of MLAs is used, then thin form factor is achieved, but precise positioning and alignment are required
Solution Approach 1:
The microlens arrays are pre-positioned and pre-aligned during manufacturing with specific spacing equal to their focal lengths. This preliminary action ensures that the optical paths and phase relationships are correctly established before the system is assembled into the final device, reducing the need for complex post-assembly alignment procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables compact, high-efficiency imaging with reduced distortions and scatter, allowing for non-contact imaging and scalability without increasing system volume, suitable for applications like fingerprint readers and microscopes.
Implementation Method 1
The first and second pairs of MLAs are separated from one another along an optical axis of the lens system by a distance D such that the first pair of MLAs is configured to provide a representation of a Fourier transform of light emanating from an object, the representation being provided along a plane disposed between the first and second pairs of MLAs, and the second pair of MLAs is configured to provide an image of the object via Fourier transformation of the representation
Implementation Method 2
a first pair of in-tandem microlens arrays, each microlens array of the first pair including a respective set of cells, each cell having a first common focal length, and a second pair of in-tandem microlens arrays, each microlens array of the second pair including a respective set of cells, each cell having a second common focal length
Data Source
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AI summary
A lens system includes a first lens array assembly including a first plurality of cells, each cell of the first plurality of cells configured to exhibit a pair of Fourier transform lenses, and a second lens array assembly including a second plurality of cells, each cell of the second plurality of cells configured to exhibit a pair of Fourier transform lenses. The first and second lens array assemblies are positioned relative to one another along an optical axis of the lens system such that an image of an object is provided at an image conjugate distance from the second lens array assembly.